3306-A bearing: complete specifications & equivalents
The 3306-A is a ISO 15 radial bearing sized 30 x 72 x 30.2 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 30 mm |
| Outer diameter D | 72 mm |
| Width B | 30.2 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 42.5 kN |
| Basic static load rating C0 | 30 kN |
| Fatigue load limit Pu | 1.27 kN |
| Reference speed (thermal) | 10000 rpm |
| Limiting speed (mechanical) | 9000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 520 g |
| Manufacturer designation | 3306 A |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & 3300-series range
| Bore d | 1.181 in |
|---|---|
| Outer diameter D | 2.835 in |
| Width B | 1.189 in |
| ISO bore code | 06 |
| Radial section height (D−d)/2 | 21 mm |
| Smallest bore in 3300-series | 15 mm |
| Largest outer diameter in 3300-series | 240 mm |
| Width range across 3300-series | 19–92.1 mm |
| Bore position in 3300-series (smallest first) | 5 of 20 |
| Bore above smallest 3300-series size | 15 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 3306-ATN9 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 30×72×30.2 mm envelope with catalogue ratings within 10 %; 3306 ATN9 is the glass-fibre PA66 cage, open arrangement execution of this size — boundary dimensions interchangeable, execution differs. |
| 3306-A-2Z | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 30×72×30.2 mm envelope with catalogue ratings within 10 %; 3306 A-2Z is the stamped steel cage, shields (-2Z) execution of this size — boundary dimensions interchangeable, execution differs. |
| 3306-A-2RS1 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 30×72×30.2 mm envelope with catalogue ratings within 10 %; 3306 A-2RS1 is the stamped steel cage, contact NBR seals (-2RS1) execution of this size — boundary dimensions interchangeable, execution differs. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 3306-A model number is decoded
3306 A is SKF's 30 mm-bore double-row angular-contact ball bearing of the 3300 series — two ball rows back-to-back for two-direction axial location in one unit, 30×72×30.2 mm. A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. with no cage suffix the double-row A execution uses the standard stamped steel ball-centred cage. Envelope 30×72×30.2 mm (1.181×2.835×1.189 in), 21.0 mm radial section height, C 42.5 kN, C0 30 kN, Pu 1.27 kN.reference speed 10,000 r/min (thermal) and limiting speed 9,000 r/min (mechanical), catalogue mass 520 g. Speed planning distinguishes the two published ceilings mechanically: the cage and balls tolerate 9,000 r/min while thermal balance under catalogue load sets the 10,000 r/min reference; at dm ≈ 51.0 mm the corresponding dn is approximately 459k mm·r/min. Envelope economics: the 30.2 mm width over a 21.0 mm section yields 1.44 mm of ring width per section millimetre, and the bearing weighs 520 g for 42.5 kN of dynamic capacity — about 12 g per rated kN. Bore-to-OD planning: OD 72 over bore 30 is a 2.40× step for this size, and the 30.2 mm width gives a bore/width ratio of 0.99; use these ratios when housing space around the 30 mm shaft is the first constraint.
Typical equipment & failure modes
Common applications
- printing and converting machinery
- gearbox input and output shafts with bidirectional thrust
- two-direction thrust positions without room for a paired single-row set
Known failure patterns
- loss of controlled axial clearance (CB) after thermal growth removes residual play
- tilted mounting that loads one double row more heavily than the other
- stamped steel cage noise and pocket wear in marginal-lubrication starts, where a brass-cage execution would survive
- mounting score marks when the bearing is cocked over a burr or keyway
- brinelling from pressing the ring home through the balls or from static overload
Selection pitfalls — read before you substitute
- The double-row 3306 takes thrust in both directions by itself — that is the reason to choose it over two single-row bearings: one housing bore, one fit, built-in set geometry.
- Catalogue ratings of 42.5/30 kN apply to the A execution; the D and DNRCBM two-piece-ring executions carry their own figures on their own pages.
- The double-row 3306 takes thrust in both directions by itself — that is the reason to choose it over two single-row bearings: one housing bore, one fit, built-in set geometry.
- Compared with a single-row pair of the same bore, the double-row 3306 occupies less axial space but offers less freedom to adjust preload — do not substitute without re-checking the arrangement.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for 3306 A as the double a steel execution; the other order numbers of the 3306 size are different products and may carry different ratings — always quote the full designation when purchasing.
Frequently asked questions
What are the dimensions and catalogue data of 3306-A?
3306 A measures 30 mm bore × 72 mm OD × 30.2 mm width (1.181 × 2.835 × 1.189 in), mass about 520 g. SKF 17000 ratings: C 42.5 kN, C0 30 kN, Pu 1.27 kN, reference speed 10,000 r/min (thermal) and limiting speed 9,000 r/min (mechanical).
What does the A suffix mean?
A on a double-row bearing means no filling slots, so both rows carry their full ball complement in both directions. with no cage suffix the double-row A execution uses the standard stamped steel ball-centred cage.
What does the D mean in A?
D marks a two-piece inner ring, used on the heavy 33-series executions to simplify mounting; the rest of the suffix identifies the cage (MA brass outer-ring-centred, M brass ball-centred, J1 stamped steel, TN9 PA66) and snap-ring/clearance options (NR, CB).
Does the 3306 double-row bearing need pairing?
No — both ball rows are built into one bearing, so bidirectional location does not require a second unit. Controlled axial clearance is part of the design rather than a field adjustment.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-27. Read our editorial & correction policy.